A review of energy dissipation mechanisms and deformation behaviors of typical mechanical metamaterials

Mechanical metamaterials are architected materials constructed from ordered assemblies of microstructural units, in which the macroscopic response is governed primarily by geometric design rather than chemical composition. This provides a straightforward route to tuning the macroscopic mechanical response through geometry design. That is, by tailoring the shape, dimensions, connectivity, and spatial arrangement of these microstructural units, mechanical metamaterials can realize extraordinary properties that are rarely attainable in conventional materials, such as negative Poisson’s ratio, negative effective mass density, and mechanical multi-stability. These unusual responses, together with their intrinsic lightweight nature, make mechanical metamaterials promising candidates for impact mitigation, blast protection, vibration attenuation, and multifunctional integration applications. In these scenarios, mechanical metamaterials are typically required to withstand static to highly dynamic loads, making energy dissipation a primary design objective. Under such load conditions, the energy dissipation primarily arises from the individual or synergistic contributions of elastic-plastic deformation, instability-triggered buckling and post-buckling evolution, crack propagation, as well as viscoelastic relaxation. Therefore, it is crucial to determine when each mechanism is activated and how they work together when designing next-generation mechanical metamaterials.To this end, this review provides a comprehensive synthesis of recent advances in the energy dissipation mechanisms and deformation behaviors across four representative classes of mechanical metamaterials: origami/kirigami structures, lattice-inspired metamaterials, chiral metamaterials, and bio-inspired architectures. The fundamental relationships among structural design, deformation mode, and energy absorption and dissipation mechanisms are systematically summarized. For origami and kirigami metamaterials, we summarize how folding kinematics, crease patterns, and self-locking constraints shape their mechanical response, enabling multi-stage deformation, snap-through transitions, quasi-zero-stiffness responses, and stable load plateaus. In these systems, energy dissipation is dominated by folding-induced rotation and plastic deformation. Lattice metamaterials exhibit stretch-dominated or bending-dominated behaviors depending on their topological configurations. In both cases, energy absorption is controlled mainly by local buckling and plastic collapse of struts. We further highlight defect-enabled and disordered lattice designs, including dislocation, twin-inspired interfaces, and controlled randomness. These features redistribute load paths and inhibit shear-band localization, which improves damage tolerance and enables more delocalized energy dissipation. For chiral metamaterials, we emphasize that auxetic and energy dissipation arise mainly from node rotation, ligament bending, and compression-twist coupling. For bio-inspired designs, we discuss how brick-and-mortar architectures, bioligand-type helicoidal laminates, interlocking interfaces, and functional gradients achieve synergistic toughening and efficient energy dissipation via crack deflection/branching, bridging, and frictional sliding across hierarchical interfaces. Furthermore, the influence of loading rate, size effect, and constituent material properties on the energy dissipation performance is discussed in detail. At high strain rates, inertial effects and rate-dependent material strengthening alter local buckling modes and energy localization behaviors, whereas structural scale effects lead to transitions between global and local failure modes. The review also highlights recent progress in AI-assisted inverse design and optimization, which accelerates the exploration of complex design spaces but still faces challenges related to data fidelity and physical interpretability. Within a framework linking structural design, dissipation mechanisms, and mechanical responses, this review elucidates structure-property correlations and guides the multi-scale design of energy-dissipative metamaterials. Overall, this review clarifies key dissipation pathways and tunability strategies, and outlines persisting scientific questions toward next-generation multifunctional protective systems.